Australian team Mitchelton-Scott's rider Simon Yates has taken his second Tour de France victory of the week, oblivious to the fireworks behind him as the battle for the yellow jersey exploded on the ramps up to the Prat d'Albis on stage 15.

Thibaut Pinot darted forward for the second day in a row as the first cracks appeared in Julian Alaphilippe's challenge, while Geraint Thomas again watched his rivals race up the road in front of him.

The only disappointment for fans at the end of 185km of entertainment on Sunday was that Monday's rest day meant they must wait for the next instalment.

In lieu of a race, Monday will instead be a chance to dissect a general classification in which only 39 seconds separate Thomas in second from Emanuel Buchmann in sixth, and in which Alaphilippe seems to accept he may no longer be a factor despite sitting 95 seconds ahead of Thomas.

Simon Yates rides during stage 15 of the Tour de France. (PA/AAP)

Australian rider Richie Porte finished 10th and cut the gap to the front by another 19 seconds in the 15th stage to be 6:30 off the overall pace.

"It's not a surprise that I'm starting to struggle," said the Deceuninck-Quick Step rider, who did not target the Tour this year but will enjoy an 11th day in yellow when the race resumes in Nimes on Tuesday.

If Alaphilippe is fading, Pinot looks the man in form of all the contenders.

Yates had no such tactical quandaries as he followed up Thursday's victory on stage 12 to Bagneres-de-Bigorre with a superb solo effort.

The Mitchelton-Scott rider, free to go stage hunting after his brother Adam saw his general classification hopes ended on the Tourmalet, was active in the breakaway before making his final decisive move with a little under nine kilometres of the final climb above Foix remaining.

"It was little bit different to the first stage win," the 26-year-old Lancastrian said.

"We really raced from the beginning to the final. It was very tough and I'm proud of what I did there."

Given Adam's struggles and Simon's form off the back of his eighth place in the Giro d'Italia, some will ask why their roles were not reversed here, but Simon suggested his stage victories were a product of not being the team leader.

"I'm racing with a different mentality," he said.

"I've not come here with any ambition for GC whatsoever. I'm very relaxed and going about it how I want."

Australian Jack Haig is 39:21 off the lead in general classification and compatriot Michael Matthews is 1:13:54 off the pace.